Reduction of E. Coli. 0157:H7 to undetectable populations in fresh ground beef has proven to be a difficult problem for the beef industry to overcome. The random, infrequent detection of the pathogens presence plagues consumers and the industry alike. Fresh ground beef is an important staple of the US consumers' diet, and its elimination is out of the question. In fact, in spite of the justifiable concern about continued contamination of ground beef, there are other fresh foods, such as vegetables and fruits, that likely have a greater incidence of pathogen contamination. Identifying a consistently reliable, consumer acceptable, and cost-effective method of achieving undetectable pathogen populations in fresh ground beef has not been successful.
The US distribution system, via which fresh beef products are delivered to American consumers must operate flawlessly, with precise refrigeration control, distribution, and inventory management to avoid significant spoilage bacteria and metmyoglobin discoloration losses. Refrigeration control in trucks has improved significantly but still some 14% of total available value is lost by retailers in the form of mark-downs and unsaleable items having lost adequate consumer appeal, even at marked down prices.
While the US distribution system is more than adequate to provide for the timely delivery of consumer beef products comprising some 86% of the value of beef consumed in the USA, the remaining 14% of lost value will remain unresolved until an improved system addresses the causes. Unfortunately, it is not always the same beef products that combine to create this 14% loss. The loss can comprise any beef items produced, but providing a reliable, adequate storage/shelf life extension for all items will resolve many of the current system shortcomings. In the battle against the combined forces that cause the 14% loss of value, it is not just the steady but relentless spoilage bacterial putrefaction effects. The 14% loss in value is often exceeded due to the consequences of pathogenic contamination of any beef products and the simple metmyoglobin discoloration of what was once bright red fresh beef adds more loss.
Metmyoglobin discoloration can be a good indicator of a lack of freshness in beef, which is why eliminating this natural indicator with the cherry red color fixing properties of carbon monoxide is an unacceptable practice to resolve the discoloration problem. Additionally, a confounding phenomenon results in premature metmyoglobin discoloration when oxygen contacting the beef comprises between about 3,000 to 30,000 ppm of any modified atmosphere contained in a package irrespective of beef age and even when the beef is still fresh. This represents another loss factor that needs resolution if the full benefits of anoxic case ready packaging are to be a benefit.
The ground beef industry uses grinding equipment that doesn't just grind the beef; the equipment emulsifies a significant proportion of the throughput that can provide protection to pathogens that become enclosed in the emulsified beef. Immediately following grinding, massive blenders that are very efficient at blending, quickly entrain atmospheric oxygen into the beef by exposing to atmosphere what was, just prior to grinding, dedoxymyoglobin, to which oxygen molecules quickly attach to produce bright red oxymyoglobin. If this “oxygenated” ground beef is then packaged in an anoxic case ready package the entrained oxygen is released (due to the lower O2 partial pressure) and will in every instance increase the oxygen content of an anoxic atmosphere to the range between 3,000 to 30,000 ppm and the resultant deleterious effects described above.
Large quantities of generally high lean content boneless beef are imported from countries such as Australia, New Zealand and Canada. The substantially disease free Australian cattle production environment combined with exceptionally well operated slaughtering facilities, has evolved to be the favored source of high lean content boneless beef for ground beef production. However, 8,000 miles of ocean separate the USA from Australia. There should be a way to displace these imports with more beef produced in the USA. A primary driver for the Australian and New Zealand high lean beef imports is the need to accommodate the large quantities of high fat content beef trim (of approximately 50% to 73% fat) comprising some 35% to 40% of US sourced ground beef raw materials, by combining high lean imports with locally produced high fat content boneless beef thereby diluting the high fat content of the locally produced boneless beef.
Hohenester et al describe a method of separation for meat in U.S. Pat. No. 5,435,443 and the disclosure provides a series of temperature ranges with corresponding pressure ranges. Hohenester et al. claim that a mixture of liquefied carbon dioxide and water-containing substances such as meat can be used to separate fat from lean by flotation and sedimentation. The temperature ranges indicated are below the freezing point of water, for example, negative 10° C., 13° C., 14° C. and 20° C. at between 15 and 50 Bar and are recited as temperatures that are below the freezing point of water and at which the density of liquid carbon dioxide can be adjusted to correspond to that of water so that water-containing substances of the mixture can be readily separated. However, water expands when frozen and water containing substances such as beef comprises some 70% water in the lean component and 10% water in tallow. The expansion of water when frozen reduces its density from 62.4 lbs per cubic foot to about 57 lbs per cubic foot, which is similar to the density of fat. At about the temperature when water freezes, the density of liquefied carbon dioxide is about 57.8 lbs per cubic foot and at 36° F. the density of liquefied carbon dioxide is about 56.9 lbs per cubic foot. Also, the majority of fat contains at least a small amount of lean and the majority lean contains a small amount of fat. Furthermore, the water content of meat varies by at least a few percentage points due to many factors including inconsistent dehydration after animal slaughter and disassembly. All of the above factors render the method of separating fat from lean using pure, liquefied carbon dioxide too inconsistent to be commercially reliable.
A need therefore still exists to more efficiently separate the lower value tallow with fat from the higher value lean beef contained in trim and to more effectively kill, reduce, or completely remove the microbial pathogenic population and to eliminate sources of cross contamination and recontamination, while also producing a ground beef product of specific fat content.